CN110339596B - Preparation method of oil-water separation composite membrane added with COFs - Google Patents
Preparation method of oil-water separation composite membrane added with COFs Download PDFInfo
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- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
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Abstract
The invention discloses a preparation method of an oil-water separation composite membrane added with COFs. The method combines the electrostatic spinning technology with the Covalent Organic Frameworks (COFs), blends the nano-fibers with good modifiability and the COFs which contain a large number of amphiphilic group hydroxyl groups and have ultrahigh porosity and ultrahigh specific surface area for modification, improves the problem of wettability of polymers in oil water, improves the roughness of the composite membrane, greatly improves the hydrophilic performance of the composite membrane, improves the flux of the composite membrane under the gravity condition, and realizes effective regulation and control of surface wettability of the membrane material, so that the super-amphiphilic, underwater super-oleophobic and underwater super-hydrophobic properties in air can be realized, the membrane can be accurately designed according to the properties of different oil-water mixtures, oil-in-water and water-in-oil mixtures can be separated simultaneously, and the application prospect of efficiently treating various industrial wastewater can be realized.
Description
Technical Field
The invention belongs to the field of preparation of oil-water separation membranes, and particularly relates to a preparation method of an oil-water separation composite membrane added with COFs.
Background
With the development of society, the demand of people on energy is increased rapidly, and the exploitation, transportation and refining of petroleum resources enter a high-speed development stage. However, the leakage of various kinds of oil stains caused by natural or man-made factors causes great harm to the global ecological environment. The presence of oil pollutants in water can isolate the exchange between the water and air and the normal incidence of sunlight, and petroleum contains a large amount of mutagenic and carcinogenic toxic hydrocarbon compounds which can be ingested by aquatic animals and plants and finally enriched in human bodies through food chains, thus seriously threatening the health of human beings. Therefore, water body oil pollution is a global problem which needs to be solved urgently. After oil stains enter a water body, oil-water mixtures of four types of floating oil, dispersed oil, emulsified oil and dissolved oil can be formed, wherein the floating oil and the dispersed oil are easy to agglomerate into a continuous oil layer due to large particle sizes, and can be easily removed by the traditional methods of adsorption, sedimentation and mechanical oil skimming; for the separation of stable emulsified oil and dissolved oil, although a certain separation effect can be obtained by the traditional demulsification technology such as a sedimentation method, a biological method, an ultra-micro-filtration membrane separation method and the like, the defects of high energy consumption and low treatment efficiency still exist. Therefore, there is a need to develop a novel high-efficiency oil-water emulsion separation material.
The electrostatic spinning nanofiber has the characteristics of small diameter, large specific surface area, good continuity, good structure adjustability and the like, and a porous membrane formed by the electrostatic spinning nanofiber has high porosity and good pore canal connectivity, and is favorable for rapid transport of a medium.
The document of application No. 201810680537.5 discloses a magnetic oil-water separation membrane, which is formed by scraping a ferroferric oxide/PAA mixed solution prepared by jointly ultrasonically treating ferroferric oxide, 4' -diaminodiphenyl ether and pyromellitic dianhydride in N, N-dimethylformamide at 70-80 ℃ on a glass plate, wherein the prepared oil-water separation membrane can only separate oil-in-water type oil-water mixed liquid but cannot separate water-in-oil type oil-water mixed liquid, and the application of the membrane material in the separation of different types of oil-water mixed liquid is limited. The composite Membrane described in the literature "Jianjiang Zhang, Xinglong Pan, Qingzhong Xue, Daliang He, Lei Zhu and Qikai Guo, anti-fouling hydrogenated polyacrylic/Graphene Oxide Membrane with dispersed-Knotted Structure for high Effective Separation of Oil-Water Emulsion, Journal of Membrane science.532(2017) 38-46" is electrospun by blending Graphene Oxide (GO) with Polyacrylonitrile (PAN). The performance reaches the best when the addition amount of GO is 7% and the good oil-water separation capability is shown. However, the composite membrane is not environmentally friendly since it needs to be hydrolyzed, and only oil-in-water type emulsion can be separated and water-in-oil type emulsion cannot be separated, limiting the range of application thereof.
Disclosure of Invention
Aiming at the defects in the prior art, the technical problem to be solved by the invention is to provide a preparation method of an oil-water separation composite membrane added with COFs.
The technical scheme for solving the technical problem is to provide a preparation method of an oil-water separation composite membrane added with COFs, which is characterized by comprising the following steps:
1) adding the substance A and the substance B into an excessive solvent, and reacting for 12-24h at the temperature of 100-120 ℃ under the catalysis of a catalyst; then washing to neutrality, and then drying to remove residual solvent to obtain COFs;
the substance A is any one of 1,3, 5-tri (4-aminobenzene) benzene or 1,3, 5-trimethylphloroglucinol; the substance B is any one of 2, 5-dihydroxy terephthalaldehyde, p-phenylenediamine or benzidine; the mass ratio of the substance A to the substance B is 1-4: 1;
the solvent is formed by compounding a solvent A and a solvent B; the solvent A is o-dichlorobenzene or mesitylene; the solvent B is dioxane, N-butanol, ethanol, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, anisole, phenethyl alcohol or toluene; the volume ratio of the solvent A to the solvent B is 1-9: 1;
2) adding the COFs obtained in the step 1) into a solvent C, and performing ultrasonic treatment to uniformly disperse the COFs; adding the polymer to dissolve completely, and defoaming to obtain a membrane casting solution;
the mass ratio of the COFs to the polymer is 0.1-3: 100; the polymer accounts for 7-15% of the total mass of the polymer and the solvent C;
3) carrying out electrostatic spinning on the casting solution obtained in the step 2) to obtain a primary membrane;
4) drying the primary membrane obtained in the step 3) to remove residual solvent, so as to obtain the oil-water separation composite membrane blended with COFs.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method combines the electrostatic spinning technology with the Covalent Organic Frameworks (COFs), blends the nano-fibers with good modifiability and the COFs which contain a large number of amphiphilic group hydroxyl groups and have ultrahigh porosity and ultrahigh specific surface area for modification, realizes effective regulation and control of the surface wettability of the membrane material, can accurately design the membrane according to the properties of different oil-water mixtures, and can simultaneously separate oil-in-water and water-in-oil mixtures.
(2) The complexes obtained by the processThe composite membrane has high porosity and high specific surface area, is beneficial to the rapid transportation of media, improves the wettability problem of polymers in oil and water by blending modification with COFs, improves the roughness of the composite membrane (the roughness is improved by more than 3 times), greatly improves the hydrophilic performance of the composite membrane, and improves the flux (the highest flux can reach 4229.29L/m) under the gravity condition of the composite membrane2h) Thereby realizing super-amphiphilic, underwater super-oleophobic and oil-immersed super-hydrophobic in the air and having the application prospect of efficiently treating various industrial wastewater.
(3) The method prepares the COFs by a hot solvent method, and compared with the existing preparation method of the COFs, the method needs to react for 3 days in a vacuum environment, the reaction condition is mild, and the reaction time is greatly shortened.
(4) The mechanical properties of the film are improved by adding COFs.
Drawings
FIG. 1 is an FTIR plot of COF-DhaTab of example 1 of the present invention.
FIG. 2 is an XRD pattern of COF-DhaTab of example 1 of the present invention.
FIG. 3 is an SEM picture of COF-DhaTab of example 1 of the present invention.
Fig. 4 is an SEM image of the composite membrane of example 1 of the present invention.
FIG. 5 is a contact angle diagram of a composite film of example 1 of the present invention.
Fig. 6 is a graph of roughness data for the film of comparative example 1.
FIG. 7 is a graph of roughness data for the composite film of example 1 of the present invention.
Fig. 8 is an experimental diagram of the underwater oil contamination resistance of embodiment 1 of the present invention.
FIG. 9 is a diagram of the experiment of the water pollution resistance under oil in example 1 of the present invention.
FIG. 10 is a graph showing tensile strengths of example 1 of the present invention and comparative example 1.
Detailed Description
Specific examples of the present invention are given below. The specific examples are only intended to illustrate the invention in further detail and do not limit the scope of protection of the claims of the present application.
The invention provides a preparation method (short for method) of an oil-water separation composite membrane added with COFs, which is characterized by comprising the following steps:
1) adding the substance A and the substance B into an excessive solvent, and reacting for 12-24h at the temperature of 100-120 ℃ under the catalysis of a catalyst of glacial acetic acid; then washing with tetrahydrofuran and ethanol to neutrality, and then drying in a vacuum oven at 60-120 ℃ for 12-24h to remove residual solvent to obtain COFs;
the COFs are specifically COF-DhaTab, COF-TpPa or COF-TpBD;
the substance A is any one of 1,3, 5-tri (4-aminobenzene) benzene or 1,3, 5-trimethylphloroglucinol; the substance B is any one of 2, 5-dihydroxy terephthalaldehyde, p-phenylenediamine or benzidine; the mass ratio of the substance A to the substance B is 1-4: 1;
the solvent is formed by compounding a solvent A and a solvent B; the solvent A is o-dichlorobenzene or mesitylene; the solvent B is dioxane, N-butanol, ethanol, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, anisole, phenethyl alcohol or toluene; the volume ratio of the solvent A to the solvent B is 1-9: 1;
2) adding the COFs obtained in the step 1) into a solvent C, and performing ultrasonic dispersion for 1-5 hours to uniformly disperse the COFs; adding the polymer, stirring for 8-24h, completely dissolving to form a homogeneous system, standing and defoaming to obtain a membrane casting solution;
the mass ratio of the COFs to the polymer is 0.1-3: 100; the polymer accounts for 7-15% of the total mass of the polymer and the solvent C;
the polymer is a polymer which can be subjected to electrostatic spinning and has excellent spinnability, and specifically is polyacrylonitrile, polyether sulfone, polyvinylidene fluoride or polystyrene;
the solvent C is a solvent capable of dissolving the polymer, and specifically is N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), Tetrahydrofuran (THF) or the like;
3) putting the casting solution obtained in the step 2) into electrostatic spinning equipment, and performing electrostatic spinning (4-8 h for spinnable yarn) under the spinning conditions of 15-25 KV voltage, 0.5-1 ml/h propelling speed, 10-15 cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
4) drying the primary membrane obtained in the step 3) in a vacuum oven with the temperature of 30-80 ℃ (preferably 60 ℃) for 12-36h (preferably 24h) to remove residual solvent, and obtaining the oil-water separation composite membrane blended with COFs.
Preferably, step 2) is: adding the COFs and PVP (polyvinylpyrrolidone) obtained in the step 1) into a solvent C, and performing ultrasonic dispersion for 1-5 hours to uniformly disperse the COFs and the PVP; adding a polymer, stirring for 8-24h, standing and defoaming to obtain a membrane casting solution; the mass ratio of PVP to the polymer is 1-4: 20.
Preferably, step 4) is: soaking the primary membrane obtained in the step 3) in water for 24-48h to wash out PVP attached to the surface of the electrostatic spinning fiber, and then carrying out a drying process to remove residual solvent to obtain the porous oil-water separation composite membrane blended with COFs.
Example 1
(1) Adding 30mg of 1,3, 5-tri (4-aminobenzene) benzene and 20mg of 2, 5-dihydroxy terephthalaldehyde into a compound solvent of 16ml of o-dichlorobenzene and 4ml of n-butyl alcohol, dripping 0.2ml of glacial acetic acid into the mixture, transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask, and reacting for 12 hours at 100 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-DhaTab.
(2) Adding 9g of DMF and 10mg of COF-DhaTab into a 100ml single-neck round-bottom flask, performing ultrasonic dispersion for 2 hours to form uniform dispersion liquid, adding 1g of polyacrylonitrile powder, stirring for 12 hours at normal temperature, standing for 24 hours, and defoaming to form stable casting solution.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 20KV voltage, 1ml/h propelling speed, 10cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and drying the primary membrane in a vacuum oven at 60 ℃ for 24 hours to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively above 99.92% and 99.9%, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively above 99.81% and 99.86%. The flux under the condition of flux gravity can reach 4229.29L/m at most2h. Roughness of 1.708 muAnd m is selected. The tensile strength was 5.2 MPa.
Test equipment for separation efficiency of oil-in-water mixture: total organic carbon content (TOC). The test method comprises the following steps: a quantity of the oil-in-water mixture is injected into a total organic carbon content meter, and the data read by the meter is the organic carbon content of the oil-in-water mixture. J ═ T (T)1-T2)/T1(ii) a J is the separation efficiency, T1Is organic carbon content (ppm), T, of oil-in-water mixture before separation2Is the organic carbon content of the separated oil-in-water mixture.
Test equipment for separation efficiency of water-in-oil mixture: karl Fischer micro-moisture meter. The test method comprises the following steps: mu.l of the water-in-oil mixture was injected into a Karl Fischer micro moisture meter, and the data read by the meter was the moisture content in the water-in-oil mixture. Q ═ Q (Q)1-Q2)/Q1(ii) a Q is the separation efficiency, Q1The water content (ppm) of the water-in-oil mixture before separation, and Q2 is the water content of the water-in-oil mixture after separation.
Testing equipment of flux: the sand core filtering device, the stopwatch, the electronic scale, the scale. The test method comprises the following steps: and (3) quickly transferring the mixture to be tested to a sand core filtering device, starting timing, weighing the filtered filtrate after 20s, and calculating according to a formula Jw (V/(AxDeltat), wherein Jw is flux, V is filtrate volume, A is effective filtering area, and Deltat is separation time.
Roughness test equipment: true color confocal microscopy. The test method comprises the following steps: the film to be measured is cut into a circular film with the diameter of about 1cm, and the circular film is placed under a true color confocal microscope lens, and the device automatically reads the number.
Tensile strength test equipment: and a tensile testing machine. The test method comprises the following steps: the film was cut into sample strips 2cm long by 1cm wide, which were placed in a tensile tester and read directly by the instrument.
As can be seen from FIG. 1, at 1642cm-1A distinct COFs stretching vibration peak (C ═ N) appears. And the stretching vibration peaks of the reactive groups C ═ O and N — H disappeared.
FIG. 2 contains XRD patterns of COF-DhaTab of example 1 and XRD patterns of two crystal forms (AA-stacking and AB-stacking) of COFs simulated by Materials Studio software; as can be seen from FIG. 2, the XRD of the COF-DhaTab of example 1 is consistent with that of AA-stacking, indicating the successful synthesis of COF-DhaTab.
As can be seen from fig. 3 and 4, the beads (composite films) in fig. 4 encapsulate the particles (COFs) in fig. 3. As can be seen from FIG. 3, the particle diameter of COF-DhaTab was approximately 400nm and the particles were uniform. As can be seen from FIG. 4, the composite film is of a bead structure, the COFs particles are uniformly distributed in the composite film, and the diameter of the electrostatic spinning fiber is about 200 nm.
Fig. 5(a) and (b) show the contact angles of water and oil in air, respectively, of the composite membrane, which is an amphiphilic membrane in air, at 0 °. Fig. 5(c) is the water contact angle under oil (water contact angle is 152.3 °), and fig. 5(d) is the oil contact angle under water (oil contact angle is 153.7 °), so the composite membrane is superhydrophobic under oil and superoleophobic under water.
Anti-contamination test equipment: needle tube, needle head, quartz glass ware. Fig. 8 is an anti-contamination test of underwater oil, fig. 8a shows the membrane under water, fig. 8b shows the injector filled with oil injecting under water onto the membrane surface, and fig. 8c shows the oil droplets floating on the membrane surface without any adhesion. Fig. 9 is an anti-contamination test of water under oil, fig. 9a shows the membrane under oil, fig. 9b shows the injector filled with water injecting under oil to the membrane surface, and fig. 9c shows the water droplets floating on the membrane surface without any adhesion.
Example 2
(1) Adding 20mg of 1,3, 5-tri (4-aminobenzene) benzene and 20mg of 2, 5-dihydroxy terephthalaldehyde into a compound solvent of 17ml of o-dichlorobenzene and 3ml of n-butyl alcohol, dripping 0.2ml of glacial acetic acid into the mixture, transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask, and reacting for 12 hours at 110 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-DhaTab.
(2) 0.15g of polyvinylpyrrolidone, 9g of DMAc and 20mg of COF-DhaTab are added into a 100ml Schlenk bottle, ultrasonic dispersion is carried out for 2 hours to form uniform dispersion liquid, 1g of polyvinylidene fluoride powder is added, stirring is carried out for 12 hours at normal temperature, standing is carried out for 24 hours, and defoaming is carried out to form stable casting solution.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 6 hours under the spinning conditions of 18KV voltage, 0.8ml/h propelling speed, 12cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and (3) soaking the primary membrane in water for 24 hours, and then drying in a vacuum oven at 70 ℃ for 36 hours to obtain the composite membrane.
The test shows that the separation efficiency of the mixture without emulsifier oil-in-water and water-in-oil is above 99.93% and 99.94% respectively, and the separation efficiency of the mixture containing emulsifier oil-in-water and water-in-oil is above 99.85% and 99.87% respectively. The flux can reach 3986.5L/m at the highest under the gravity condition2h. The roughness was 1.736 μm. The tensile strength was 5.1 MPa.
Example 3
(1) Adding 65mg of 1,3, 5-trimethylbenzene trisol and 20mg of p-phenylenediamine into a compound solvent of 3ml of phenethyl alcohol and 17ml of mesitylene, then dripping 0.2ml of glacial acetic acid into the mixture, and transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask to react for 15 hours at 120 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-TpPa.
(2)9g of DMSO and 30mg of COF-TpPa are added into a 100ml single-neck round-bottom flask, ultrasonic dispersion is carried out for 5 hours to form uniform dispersion liquid, 1.1g of polyacrylonitrile powder is added, stirring is carried out for 24 hours at normal temperature, standing is carried out for 24 hours, and defoaming is carried out to form stable casting liquid.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 18KV voltage, 0.8ml/h propelling speed, 15cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and drying the primary membrane in a vacuum oven at 60 ℃ for 18h to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively above 99.95 percent and 99.94 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively above 99.87 percent and 99.86 percent. The flux under the gravity condition can reach 3743.4L/m at most2h. The roughness was 1.936. mu.m. The tensile strength was 4.1 MPa.
Example 4
1) Adding 50mg of 1,3, 5-trimethylbenzene and 20mg of benzidine into a compound solvent of 16ml of o-dichlorobenzene and 4ml of phenethyl alcohol, then dripping 0.2ml of glacial acetic acid into the solvent and transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask to react for 24 hours at 120 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-TpBD.
(2)0.2g of polyvinylpyrrolidone, 9g of DMAc and 20mg of COF-TpBD are added into a 100ml single-neck round-bottom flask, ultrasonic dispersion is carried out for 2 hours to form uniform dispersion liquid, 1g of polyvinylidene fluoride powder is added, stirring is carried out for 8 hours at normal temperature, and standing is carried out for 24 hours to defoam to form stable casting solution.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 8 hours under the spinning conditions of 20KV voltage, 0.5ml/h propelling speed, 12cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and (3) soaking the primary membrane in water for 24 hours, and then drying in a vacuum oven at 80 ℃ for 36 hours to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively more than 99.91 percent and 99.93 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively more than 99.8 percent and 99.84 percent. The flux under the gravity condition can reach 4243.6L/m at most2h. The roughness was 1.737 μm.
Example 5
(1) Adding 30mg of 1,3, 5-tri (4-aminobenzene) benzene and 20mg of 2, 5-dihydroxy terephthalaldehyde into a compound solvent of 18ml of o-dichlorobenzene and 2ml of n-butyl alcohol, dripping 0.2ml of glacial acetic acid into the mixture, transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask, and reacting for 12 hours at 100 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-DhaTab.
(2) Adding 9g of DMAc and 20mg of COF-DhaTab into a 100ml single-neck round-bottom flask, performing ultrasonic dispersion for 2 hours to form uniform dispersion liquid, adding 1g of polyether sulfone powder, stirring for 12 hours at normal temperature, standing for 24 hours, and defoaming to form stable casting liquid.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 20KV voltage, 0.7ml/h propelling speed, 14cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and (3) drying the primary membrane in a vacuum oven at 60 ℃ for 20h to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively more than 99.95 percent and 99.96 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively more than 99.9 percent and 99.91 percent. The flux under the gravity condition can reach 4013.6L/m at most2h. The roughness was 1.774 μm. The tensile strength was 4.8 MPa.
Example 6
(1) Adding 40mg of 1,3, 5-trimethylbenzene triphenol benzene and 20mg of benzidine into a compound solvent of 10ml of dioxane and 10ml of mesitylene, dripping 0.2ml of glacial acetic acid into the mixture, and transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask to react for 12 hours at 120 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-TpBD.
(2) Adding 9g of DMAc and 10mg of COF-TpBD into a 100ml single-neck round-bottom flask, performing ultrasonic dispersion for 2 hours to form uniform dispersion liquid, adding 1g of polyvinylidene fluoride powder, stirring at normal temperature for 18 hours, standing for 24 hours, and defoaming to form stable casting liquid.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 15KV voltage, 0.8ml/h propelling speed, 13cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and drying the primary membrane in a vacuum oven at 60 ℃ for 18h to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water mixture and the oil-in-water mixture is respectively above 99.9 percent and 99.92 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water mixture and the oil-in-water mixture is respectively above 99.7 percent and 99.74 percent. The flux under the gravity condition can reach 4223.6L/m at most2h. The roughness was 1.636 μm.
Example 7
(1) Adding 38mg of 1,3, 5-tri (4-aminobenzene) benzene and 22mg of 2, 5-dihydroxy terephthalaldehyde into a compound solvent of 12ml of mesitylene and 8ml of dioxane, dripping 0.2ml of glacial acetic acid into the mixture, and transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask to react for 18 hours at 100 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-DhaTab.
(2)9g of THF and 25mg of COF-DhaTab are added into a 100ml single-neck round-bottom flask, ultrasonic dispersion is carried out for 2 hours to form uniform dispersion liquid, 0.9g of polystyrene powder is added, stirring is carried out at normal temperature for 12 hours, standing is carried out for 24 hours, and defoaming is carried out to form stable casting liquid.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 5 hours under the spinning conditions of 22KV voltage, 1ml/h propelling speed, 15cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and (3) drying the primary membrane in a vacuum oven at 40 ℃ for 36h to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively above 99.89 percent and 99.9 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively above 99.76 percent and 99.8 percent. The flux under the gravity condition can reach 3765.3L/m at most2h. The roughness was 1.673 μm.
Example 8
(1) Adding 42mg of 1,3, 5-trimethylbenzene trisenol and 22mg of p-phenylenediamine into a compound solvent of 10ml of o-dichlorobenzene and 10ml of dioxane, then dripping 0.2ml of glacial acetic acid into the mixed solvent, transferring the mixed solvent into a Schlenk bottle or a single-neck round-bottom flask, and reacting for 12 hours at 100 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-TpPa.
(2)9g of DMSO and 22mg of COF-TpPa are added into a 100ml single-neck round-bottom flask, ultrasonic dispersion is carried out for 2 hours to form uniform dispersion liquid, 1g of polyacrylonitrile powder is added, stirring is carried out for 24 hours at normal temperature, standing is carried out for 24 hours, and defoaming is carried out to form stable casting liquid.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 20KV voltage, 0.8ml/h propelling speed, 15cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and drying the primary membrane in a vacuum oven at 60 ℃ for 24 hours to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively above 99.9 percent and 99.94 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively above 99.82 percent and 99.85 percent. The flux under the gravity condition can reach 3976.4L/m at most2h. The roughness was 1.686 μm.
Example 9
(1) Adding 42mg of 1,3, 5-tri (4-aminobenzene) benzene and 22mg of 2, 5-dihydroxy terephthalaldehyde into a compound solvent of 12ml of mesitylene and 8ml of dioxane, dripping 0.2ml of glacial acetic acid into the mixture, and transferring the mixture into a Schlenk bottle or a single-neck round-bottom flask to react for 12 hours at 100 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-DhaTab.
(2)0.2g of polyvinylpyrrolidone, 9g of DMF and 22mg of COF-DhaTab are added into a 100ml single-neck round-bottom flask, ultrasonic dispersion is carried out for 1h to form uniform dispersion liquid, 1g of polyacrylonitrile powder is added, stirring is carried out for 12h at normal temperature, standing is carried out for 24h, and defoaming is carried out to form stable casting solution.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 25KV voltage, 1ml/h propelling speed, 10cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and (3) soaking the primary membrane in water for 36h, and then drying in a vacuum oven at 70 ℃ for 36h to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively above 99.92% and 99.96%, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively above 99.81% and 99.84%. The flux under the gravity condition can reach 4026.8L/m at most2h. The roughness was 1.759 μm.
Example 10
1) Adding 30mg of 1,3, 5-trimethylbenzene and 20mg of benzidine into a compound solvent of 4ml of dioxane and 16ml of o-dichlorobenzene, then dripping 0.2ml of glacial acetic acid into the mixed solvent, and transferring the mixed solvent into a Schlenk bottle or a single-neck round-bottom flask to react for 12 hours at 100 ℃; washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-TpBD.
(2) Adding 9g of DMAc and 10mg of COF-TpBD into a 100ml single-neck round-bottom flask, performing ultrasonic dispersion for 2 hours to form uniform dispersion liquid, adding 1g of polyvinylidene fluoride powder, stirring at normal temperature for 12 hours, standing for 24 hours, and defoaming to form stable casting liquid.
(3) Putting the membrane casting solution into a 5ml injector, and performing electrostatic spinning for 4 hours under the spinning conditions of 20KV voltage, 1ml/h propelling speed, 12cm receiving distance, 25 +/-5 ℃ temperature and 45 +/-5% humidity to obtain a primary membrane;
(4) and drying the primary membrane in a vacuum oven at 60 ℃ for 18h to obtain the composite membrane.
The test shows that the separation efficiency of the mixture liquid of the emulsifier-free oil-in-water and the water-in-oil is respectively above 99.9 percent and 99.92 percent, and the separation efficiency of the mixture liquid of the emulsifier-containing oil-in-water and the water-in-oil is respectively above 99.78 percent and 99.8 percent. The flux under the gravity condition can reach 3836.2L/m at most2h. The roughness was 1.728 μm.
Comparative example 1
Exactly the same as example 1, with the difference that there is no COFs synthesis step and no addition of COFs.
The test shows that the separation efficiency of the mixture liquid of oil-in-water and water-in-oil without emulsifier is about 65% and 68%, and the separation efficiency of the mixture liquid of oil-in-water and water-in-oil with emulsifier is about 42% and 36%. The flux under the gravity condition can reach 1120.4L/m at most2h. The roughness was 0.559. mu.m. The tensile strength was 3.6 MPa. It can be seen that comparative example 1 did not perform oil-water separation.
As can be seen from fig. 6 and 7, the roughness of the composite film of example 1 was increased from Ra of 0.559 μm to Ra of 1.708 μm of comparative example 1, indicating that the roughness of the composite film was significantly improved. In general, wettability is related to surface roughness and surface chemical composition. According to the Wenzel model, the affinity of substances increases with increasing surface roughness due to capillary effects.
As can be seen from fig. 10, the tensile strength of the composite film of example 1 is higher, indicating that the introduction of COFs improves the tensile strength of the film.
Comparative example 2
The amount of COF-DhaTab added in step 2) was changed to 2mg, and the other operation was the same as in example 2.
Tests show that the addition amount of COF-DhaTab in the composite membrane is small, and the separation efficiency of the composite membrane on emulsifier-containing oil-in-water and water-in-oil mixed liquor is only 48% and 51%, so that oil-water separation cannot be realized.
Comparative example 3
The preparation method of COF-TpBD in step 1) adopts a mechanical grinding method, and the rest is the same as that of example 6.
Preparing COF-TpBD by adopting a mechanical grinding method: 40mg of 1,3, 5-trimethylphloroglucinol and 20mg of benzidine were added to a mortar and mechanically ground for 12 hours. Washing the obtained product with tetrahydrofuran and ethanol to neutrality, and finally drying at 60 ℃ to obtain COF-TpBD.
The composite membrane of comparative example 3 was tested to have separation efficiencies of only 56% and 48% for emulsifier-containing oil-in-water and water-in-oil mixtures, respectively, and thus oil-water separation was not possible.
Comparative example 4
COF-Dhatab in example 9 was replaced with COF-1 (disclosed in documents "A.P.Co ^ te ', A.I.Benin, N.W.Ockwig, M.O' Keeffe, A.J.Matzger, and O.M.Yaghi, Science,2005,310, 1166-.
Comparative example 4 shows separation efficiencies of about 78% and 64% for the oil-in-water and water-in-oil mixtures without emulsifier, and about 60% and 48% for the oil-in-water and oil-water mixtures with emulsifier. The flux under the gravity condition can reach 1627.6L/m at most2h. The roughness was 1.627. mu.m.
Nothing in this specification is said to apply to the prior art.
Claims (9)
1. A preparation method of an oil-water separation composite membrane added with COFs is characterized by comprising the following steps:
1) adding the substance A and the substance B into an excessive solvent, and reacting for 12-24h at the temperature of 100-120 ℃ under the catalysis of a catalyst; then washing to neutrality, and then drying to remove residual solvent to obtain COFs;
the substance A is 1,3, 5-tri (4-aminobenzene) benzene or 1,3, 5-trimethylphloroglucinol; the substance B is 2, 5-dihydroxy terephthalaldehyde, p-phenylenediamine or benzidine; when the substance A is 1,3, 5-tri (4-aminobenzene) benzene, the substance B is 2, 5-dihydroxy terephthalaldehyde; when the substance A is 1,3, 5-trimethylphloroglucinol, the substance B is p-phenylenediamine or benzidine; the mass ratio of the substance A to the substance B is 1-4: 1;
the solvent is formed by compounding a solvent A and a solvent B; the solvent A is o-dichlorobenzene or mesitylene; the solvent B is dioxane, N-butanol, ethanol, tetrahydrofuran, N-dimethylformamide, N-dimethylacetamide, anisole, phenethyl alcohol or toluene; the volume ratio of the solvent A to the solvent B is 1-9: 1;
2) adding the COFs obtained in the step 1) into a solvent C, and performing ultrasonic treatment to uniformly disperse the COFs; adding the polymer to dissolve completely, and defoaming to obtain a membrane casting solution;
the mass ratio of the COFs to the polymer is 0.1-3: 100; the polymer accounts for 7-15% of the total mass of the polymer and the solvent C;
3) carrying out electrostatic spinning on the casting solution obtained in the step 2) to obtain a primary membrane;
4) drying the primary membrane obtained in the step 3) to remove residual solvent, so as to obtain the oil-water separation composite membrane blended with COFs.
2. The method according to claim 1, wherein in step 1), the catalyst is glacial acetic acid.
3. The method for preparing oil-water separation composite membranes with COFs added according to claim 1, wherein the reactants of step 1) are washed to be neutral by tetrahydrofuran and ethanol.
4. The method for preparing an oil-water separation composite membrane added with COFs according to claim 1, wherein the drying process in the step 1) is drying in a vacuum oven at 60-120 ℃ for 12-24 h.
5. The method according to claim 1, wherein the COFs in step 1) is COF-DhaTab, COF-TpPa or COF-TpBD.
6. The method for preparing an oil-water separation composite membrane added with COFs according to claim 1, wherein in the step 3), the membrane casting solution is placed in an electrostatic spinning device, and electrostatic spinning is carried out for 4-8 hours under the conditions that the voltage is 15-25 KV, the propelling speed is 0.5-1 ml/h, the receiving distance is 10-15 cm, the temperature is 25 +/-5 ℃ and the humidity is 45 +/-5%, so as to obtain a primary membrane.
7. The method for preparing the oil-water separation composite membrane added with COFs according to claim 1, wherein the step 2) is as follows: adding the COFs and the PVP obtained in the step 1) into a solvent C, and performing ultrasonic treatment to uniformly disperse the COFs and the PVP; adding the polymer to dissolve completely, and defoaming to obtain a membrane casting solution; the mass ratio of PVP to the polymer is 1-4: 20;
step 4) is: washing out PVP attached to the surface of the primary membrane fiber obtained in the step 3), and then performing a drying process to obtain the porous oil-water separation composite membrane blended with COFs.
8. The method according to claim 1 or 7, wherein in step 2), the polymer is a polymer capable of being electrospun; the solvent C is a solvent capable of dissolving the polymer.
9. The method for preparing an oil-water separation composite membrane added with COFs according to claim 1 or 7, wherein the drying process in the step 4) is drying in a vacuum oven at 30-80 ℃ for 12-36 h.
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| CN111760474B (en) * | 2020-07-17 | 2022-05-03 | 天津工业大学 | Preparation method of COFs @ HPAN nanofiltration composite membrane |
| CN113019138A (en) * | 2021-03-12 | 2021-06-25 | 北京化工大学常州先进材料研究院 | Preparation and application of PEI @ COF composite film |
| CN114570067A (en) * | 2022-02-24 | 2022-06-03 | 福州大学 | COF-F constructed super-hydrophobic fabric membrane and preparation method and application thereof |
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